VideoAdjustable qualityRuns in your browser

Change Video Speed

Speed a video up or slow it down, from slow motion to a 4× time-lapse, with the sound kept in step and in tune. Some detail is discarded to fit the target format; how much depends on the format and your settings.

Not uploaded to any serverConverted on this deviceGone when you close the tabHow this works

Drop your files here

MP4, MOV, MKV, WebM and 7 more formats · up to 512 MB each

or paste files from your clipboard

Ready when you are

Speed a video up or slow it down, from slow motion to a 4× time-lapse, with the sound kept in step and in tune. Everything happens in this tab; nothing is sent anywhere.

⌘K to search converters

How to use it

1
Add your files
Change Video Speed works with MP4, MOV, MKV, WebM, AVI, TS, 3GP, FLV, WMV, MPEG and OGV. Drop them in, browse for them, or paste from your clipboard.
2
Choose your options
Tune codec, resolution and bitrate — or leave the defaults, which are sensible.
3
Run it and download
Press the button and save the result. Everything happens on your device, and nothing is uploaded.

Privacy, in plain words

Is it safe? Your video file is not uploaded anywhere

What “uploaded” normally means. On most online converters, pressing the button copies your file across the internet onto a computer owned by that website. That copy is what the word “upload” means, and it is the part nobody explains.

What happens instead. This site does not do it. There is no server here that receives files, so your video file is read, converted and handed back by the browser you are using right now. It never travels — so there is no copy to store, read, leak or hand over.

Check it yourself in ten seconds

Turn off your Wi-Fi after this page has loaded, then convert a file anyway. It still works, because everything needed is already on your device.

The longer explanation of how this works, and the full detail of what is and is not stored on the privacy page.

Why this matters more than it sounds

Video is the format where the thing being converted is usually a recording of people, and often of people who did not expect a third party to have a copy. It matters more than it sounds, because of what video files usually are:

Unreleased footage

material under embargo or still being edited

Recorded meetings and calls

everything said, by everyone in the room

Interviews

sources and participants who consented to you, not to a website

Security-camera footage

your home or premises, and who was in it

A file that is never sent cannot be kept, leaked, subpoenaed or used to train anything. That is a property of how this works, not a promise about how carefully it is run.

Slow motion, time-lapse, and keeping the sound in step

Changing a video's speed means changing when each frame is shown. At 2× every frame is shown for half as long, so a two-minute clip plays in one; at 0.5× each is held twice as long. The frames themselves are unchanged, which is why slowing down a normal 30 fps recording looks smooth only up to a point — there are no extra frames in between to show.

The sound is retimed by the same amount so it stays in sync, using a method that keeps voices at their natural pitch. For a time-lapse, where the sound would only be a blur, you can drop it instead.

Real slow motion needs a fast camera: Footage shot at 120 or 240 fps slows down beautifully, because the frames were captured. Ordinary 30 fps footage at quarter speed will look like a slideshow.
Sped-up files are smaller: Fewer seconds of video means fewer bytes. A 4× time-lapse is roughly a quarter the size of the original at the same quality.

About these formats

Accepts

MPEG-4 Part 14

The default video container of the internet.

Extensions: .mp4, .m4v
MIME type: video/mp4
Best for: Sharing anywhere · Streaming · Social media
Compatibility: Plays on effectively every device.

Accepts

QuickTime Movie

Apple's QuickTime container, common from iPhones and cameras.

Extensions: .mov, .qt
MIME type: video/quicktime
Best for: Apple ecosystem · Video editing
Compatibility: Excellent on Apple, patchy on Windows and Android.

Good to know

Change Video Speed — questions

How does Change Video Speed work?

Speed a video up or slow it down, from slow motion to a 4× time-lapse, with the sound kept in step and in tune. Add your files above, adjust anything you want to change, and press the button. The result downloads straight to your device.

Is Change Video Speed safe — are my files uploaded to a server?

No, nothing is uploaded. On most online tools, pressing the button copies your file across the internet onto a computer owned by that website, where it is processed and then sent back. That copy is what "upload" means. This tool does not do it: your file is read and processed by the browser you are using right now, stays on this device the whole time, and is discarded when you close the tab. Turn off your Wi-Fi after the page loads and it still works, which is the quickest way to confirm it.

Can I use this on confidential or personal documents?

Yes — that is the case it was built for. Because the file never leaves your device, a confidential document is no more exposed than it is sitting in your own folder: there is no transfer, no copy on anybody else's hardware, no retention period and no staff with access. Nothing about the file is logged either — not its name, not its size, not its contents.